Some conventional work vehicles such as agricultural vehicles typified by tractors and combine harvesters and construction machines typified by crawler cranes include a work vehicle including two hydraulic stepless transmissions (HSTs) to which a driving force is transmitted from an engine, and each of the two HSTs outputs a straight-traveling force and a turning force based on an engine output. The inventor of this application previously proposed, in Patent Literature 1 (PTL 1), a work vehicle in which a straight-traveling force and a turning force output from each of the two HSTs are combined by left and right planetary gear mechanisms so that the work vehicle can turn.
Some conventional work vehicles include a work vehicle in which a hydromechanical transmission (HMT) having a transmission efficiency higher than that of an HST is housed in a transmission case to which a driving force is transmitted from an engine. The inventor previously proposed, in Patent Literature 2 (PTL 2), an in-line hydromechanical transmission in which a hydraulic pump and a hydraulic motor are disposed in line in such a manner that an input shaft of the hydraulic pump and an output shaft of the hydraulic motor are disposed concentrically.
In the in-line hydromechanical transmission, the output shaft is relatively rotatably fitted onto the input shaft to which a driving force is transmitted from the engine. A hydraulic pump, a cylinder block, and a hydraulic motor are also fitted onto the input shaft. The cylinder block alone is used for both the hydraulic pump and the hydraulic motor, and a driving force is transmitted from the hydraulic motor to the output shaft. Thus, unlike a typical hydromechanical transmission, the in-line hydromechanical transmission can combine a shifted driving force by hydraulic pressure and a driving force of the engine without interposition of planetary gear mechanisms so that high power transmission efficiency can be obtained advantageously.
Patent Literature 3 (PTL 3) proposes, as a conventional technique, a work vehicle using a parking brake and a main transmission lever in cooperation with each other. The work vehicle of PTL 3 is configured to stop a vehicle body by a two-stage pedal operation without a conflict between a driving force of a hydraulic transmission and a braking force of a parking brake. Patent Literature 4 (PTL 4) proposes, as a conventional technique, a work vehicle that uses a two-stage pedal operation to perform a first-stage braking operation of stopping traveling by setting a transmission arm of a hydraulic transmission neutral and a second-stage braking operation of stopping traveling by actuating a brake mechanism.